Discontinuous dewetting dynamics of highly viscous droplets on chemically heterogeneous substrates

Jiatong Jiang, Frankie Jackson, Suparit Tangparitkul, Mark C.T. Wilson, David Harbottle

Research output: Contribution to journalArticlepeer-review

Abstract

Hypothesis: Droplet spreading on heterogeneous (chemical/structural) surfaces has revealed local disturbances that affect the advancing contact line. With droplet dewetting being less studied, we hypothesize that a receding droplet can be perturbed by localized heterogeneity which leads to irregular and discontinuous dewetting of the substrate. Experiments: The sessile drop method was used to study droplet dewetting at a wettability boundary. One-half of a hydrophilic surface was hydrophobically modified with either i) methyloctyldichlorosilane or ii) clustered macromolecules. A Lattice Boltzmann method (LBM) simulation was also developed to determine the effect of contact angle hysteresis and boundary conditions on the droplet dynamics. Findings: The two surface treatments were optimized to produce comparable water wetting characteristics. With a negative Gibbs free energy on the hydrophilic-half, the oil droplet receded to the hydrophobic-half. On the silanized surface, the droplet was pinned and the resultant droplet shape was a distorted spherical cap, having receded uniformly on the unmodified surface. Modifying the surface with clustered macromolecules, the droplet receded slightly to form a spherical cap. However, droplet recession was non-uniform and daughter droplets formed near the wettability boundary. The LBM simulation revealed that daughter droplets formed when θR > 164°, with the final droplet shape accurately described by imposing a diffuse wettability boundary condition.

Original languageEnglish
Pages (from-to)345-356
Number of pages12
JournalJournal of Colloid and Interface Science
Volume629
Issue numberPart B
Early online date23 Sep 2022
DOIs
Publication statusE-pub ahead of print - 23 Sep 2022
Externally publishedYes

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